The invention finds application in particular, but not exclusively, in lighting and/or signaling systems which include actuators provided for adjusting the tilt angle of the headlamps as a function of attitude variations of the vehicle.
Actuators 1D and 1G of the type mentioned above are shown schematically in FIG. 1A which shows a first type of actuator control device according to the known prior art of the inventive entity. The device shown in FIG. 1A is designed for manual correction of the tilt angle of the headlamps, by means of a potentiometer which is accessible to the driver of the vehicle.
The actuators 1D and 1G respectively equip the right and left headlamps of the motor vehicle.
As shown in FIG. 1A, the actuator 1D, 1G comprises a DC motor 10, a motion conversion mechanism 11 and a motor control circuit 12.
The motion conversion mechanism 11 is for example of the wheel/worm or wheel/rack type. The rotation of the motor 10 gives rise to a linear movement of a control rod 110 which is mechanically coupled to the headlamp, so as to adjust the tilt angle of the latter.
In this type of device, the position of the rod is determined by the value of a DC setpoint voltage Vc which is applied to an input of the motor control circuit 12. The setpoint voltage Vc is processed by the motor control circuit 12 so as to shape a drive signal adapted to the motor.
The control voltage Vc is obtained by means of an adjustment potentiometer 2 which is supplied by a DC voltage Vcode. In a conventional manner, the DC voltage Vcode is present when the lighting control stalk switch is positioned at “low beam” or “full beam” by the driver of the vehicle. The voltage Vcode is also used as a supply voltage for the actuators 1D and 1G.
In this first type of actuator control device according to the prior art, the setpoint voltage Vc is applied to the actuators 1D, 1G for the entire duration that the headlamps are set to “low beam” or “full beam”, and its value is taken into account throughout this duration for controlling the actuators 1D, 1G. This means that fluctuations in the setpoint voltage Vc, due for example to parasitic electrical or electromagnetic signals, are continuously passed to the actuators 1D, 1G and give rise to undesirable displacements thereof.
These undesirable displacements of the actuators have negative repercussions on the service life thereof and may lead to tilt angle settings which do not comply with the regulations.
A second type of actuator control device according to the known prior art of the inventive entity is shown in FIG. 1B. The device shown is designed for automatic correction of the tilt angle of the headlamps.
In this second type of device, the actuators 1D and 1G are no longer controlled by a DC setpoint voltage but rather by a pulse control signal Vcpwm of the pulse width modulation type. The control signal Vcpwm is processed by a motor control circuit 12′ which is able to shape a drive signal adapted to the motor. As in the device of FIG. 1A, the actuators 1D and 1G are supplied by the DC voltage Vcode.
In the device of FIG. 1B, the control signal Vcpwm is produced by a correction control circuit 3 on the basis of front 4AV and rear 4AR attitude sensors which are coupled for example to the axles of the vehicle. The correction control circuit 3 is supplied by the DC voltage Vcode.
On account of the pulse width modulation of the control signal Vcpwm, this second type of device provides better resistance to electrical and electromagnetic parasites compared to the device of FIG. 1A. However, such a technical solution still does not make it possible to satisfy the increased requirements in terms of reliability and service life which apply to headlamps in the motor vehicle sector.